The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor, to the extent it is described in this background section, as well as aspects of the description, which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Active millimeter wave imaging systems are being used at checkpoints for screening humans for security reasons. These systems illuminate a human target with millimeter wave radiation, generally in a range from 1-500 GHz, and collect signals reflected off a body. These signals are used to generate an image of a human target for the purposes of detecting threat objects, such as guns, knives, explosives, drugs, etc.
Generally millimeter wave images are contrast (grayscale) images. In order to ensure that an active millimeter wave imaging system is able to accurately detect a threat object, it is helpful to determine whether or not the imaging system can resolve differences in grayscale between a variety of human targets and an object of interest.